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Re: http TRACE option
From: Chris McNab <chris.mcnab () trustmatta com>
Date: Fri, 18 Jan 2008 18:52:14 +0000


Here's the HTTP TRACE discussion from the 2nd edition of my book (http://www.oreilly.com/catalog/9780596510305/)

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TRACE vulnerabilities

If the TRACE method is supported and the web server is running a poorly written application that is vulnerable to cross-site scripting (XSS), a cross-site tracing (XST) attack can be launched to compromise user cookie and session information. If the web server is running a static site with no server-side application or processing of user data, the impact of TRACE support is significantly reduced.

Enhancements to the security of web browsers and clients (such as Internet Explorer 6 SP1 and later) mean that standard XSS attacks are no longer widely effective. XST is an attack class developed by Jeremiah Grossman in 2003 that allows authentication details presented in HTTP headers (including cookies and base64-encoded authentication strings) to be compromised using a combination of XSS, client-side weaknesses, and support for the HTTP TRACE method server-side. Grossman developed the attack class in response to the enhanced security mechanisms introduced by Microsoft in Internet Explorer 6 SP1, which meant that the effectiveness of XSS was significantly reduced.

Papers discussing XST can be found at the following locations:


XST depends on the following to launch an effective remote attack:

Domain restriction bypass; The ability for a client-side script to bypass browser security policy settings and send data to web sites outside the domain that is being accessed

HTTP request-enabling technologies; Support for scripting languages client-side that can establish outbound HTTP connections (to push the stolen authentication credentials to a given location)

TRACE method support; The target web server that supports the TRACE method

Upon finding and seeding an XSS bug within the target web site, we call scripting languages client-side that perform a TRACE to the web server, and then push the output to our malicious server.

Good background information relating to basic XSS attacks can be found at the following locations:


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Hope that helps,


pentestr wrote:
what is the issue if TRACE option is enabled in web servers ? Nessus results always display it as warning.
any idea...

Thanks in advance.

Chris McNab
Technical Director

Matta Consulting Limited
Falstaff House
34 Bardolph Road
Richmond upon Thames

T: 08700 77 11 00
W: www.trustmatta.com

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